An initial 4.8 million websites from the UK domain will be harvested over the next three months, following years of planning and £3 million of investment.

''If you want a picture of what life is like today in the UK you have to look at the web,'' said project lead Lucie Burgess. "We have already lost a lot of material, particularly around events such as the 7/7 London bombings or the 2008 financial crisis.

''That material has fallen into the digital black hole of the 21st century because we haven't been able to capture it. Most of that material has already been lost or taken down. The social media reaction has gone.''

Other institutions involved in the project include the National Libraries of Scotland and Wales, the Bodleian Libraries in Oxford, the University Library, Cambridge and the Library of Trinity College, Dublin.

The project came about following revisions to UK copyright law, handing the British Library the right to store a copy of every UK electronic publication on the web.

''Legal deposit arrangements remain vitally important. Preserving and maintaining a record of everything that has been published provides a priceless resource for the researchers of today and the future," said Culture Minister Ed Vaizey.

''So it's right that these long-standing arrangements have now been brought up to date for the 21st century, covering the UK's digital publications for the first time.''

Access to the digital material will be available in the reading rooms of each legal deposit library.